Patent CA-1089108-A (CA)
Inventor: AMMON J PRESTON
IPC: H05K1/18
Filed: 1977-08-19
Granted: 1980-11-04
Abstract: ABSTRACT OF THE DISCLOSURE      A metal voltage plate is drilled or punched first with alignment holes, placed upon a jig and drilled with contact clearance holes in preselected locations.  A metal ground plate is also drilled or punched first with alignment holes, placed upon a jig and drilled with contact clearance holes in preselected locations.  The clearance holes are preferably in the range of 80-90 mils in diameter and located in posi-tions where contacts are to pass through a plate without making electrical connection therewith.  Next, both the voltage and ground plates are coated, including the inner walls of the clearance holes, with a relatively thick layer of an insulative dielectric material, such as teflon, poly-urethane, p.v.c., or the like.  The coated voltage plate is then drilled or punched with an array of smaller connecting holes on the order of 40 mils in diameter, through which contacts to be electrically connected with voltage will be pressed.  Since the connecting holes are made after the plate has been coated with a dielectric, the insides of the connecting holes will comprise bare metal and, hence, make good electrical connection with a contact portion press fitted therein.  The coated ground plate is similarly drilled or punched with an array of smaller con-necting holes, also on the order of 40 mils in diameter, through which contacts to be electrically connected with ground poten-tial will be pressed.  Each connecting hole in the ground plate is in a different location, with respect to the alignment holes, than each connecting hole in the voltage plate.      A pair of double-sided, glass-filled, epoxy resin printed circuit boards, with alignment holes corresponding to those in the metal plates, are placed one above and one below the pair of adjacent metal plates.  The printed circuit boards include plated-through holes in each location where a contact is to be fitted and each corresponds to a connecting hole in either the ground or voltage plate or a clearance hole in either or both. When a contact is press fitted down through the axially aligned holes in the stacked layers, frictional engagement of the con-tacts with the plated walls of the holes in the top and the bot-tom printed circuit boards, as well as the connecting holes in the metal plates, mechanically joins the layers into a single unitary structure and electrically interconnects each point which is in interfering engagement with the contact.      The invention relates to the manufacture of multi-layer printed circuit boards and, more particularly, to a multi-layer printed circuit board having ground and voltage distribu-tion plates formed integrally therein.  The invention includes a structure and a method for manufacturing a multi-layer printed circuit board from a stack of single layer printed circuit boards and ground and voltage distribution plates.      In the past, one technique for manufacturing multi-layer printed circuit boards includes sandwiching an insulating sheet between a plurality of single layer printed circuit boards. Each of the single layer boards includes enlarged pad areas thereon which are in spaced alignment with one another.  An adhesive is placed between each one of the individual layers and then the boards are temperature and pressure laminated together to form a single, unitary, multi-layer printed circuit board. After lamination, the pad areas on the board are drilled through and the material forming the insulative board is then etched back from the hole to ensure all copper layers extend out into the hole so that subsequent plating makes electrical connection with all layers.  The drilled hole is then plated through all the layers of the board to electrically interconnect the printed circuitry formed on each one of the individual layers.